Object detection systems have been developed to alert motor vehicle operators to the presence of another moving vehicle in a monitored zone that extends behind the side mounted vehicle mirror. The monitored zone of interest is commonly referred to as the “blind spot.” Conventional side object detection (SOD) systems use an optical transmitter to transmit detection beams through a transmitter lens into the monitored zone, a receiver to receive detection beams that pass through a receiver lens after being reflected from an object in the monitored zone, and a system board that contains electronic hardware and software for generally controlling the system, including processing the received signals. The system board is electrically coupled to a vehicle electrical bus.
In many SOD systems, multiple detection or sensing beams are transmitted into the monitored detection zone from a light source that uses multiple edge emitting laser diodes. One or more photo-detectors are aimed into the monitored zone so that they will receive any reflection of the detection beams from an object in the monitored zone. Such systems typically use triangulation or phase shifts in the received reflections to discriminate between light reflected from objects within the monitored zone and light emanating from beyond the boundaries of the monitored zone. Examples of such systems are disclosed in U.S. Pat. Nos. 5,463,384 and 6,377,167, the contents of which are incorporated by reference.
Laser-type infrared light sources are preferred for many SOD systems, particularly edge emitting laser diodes. However, these edge emitting laser diodes produce a diffuse, elliptical beam, the reflections of which are very difficult to detect and analyze. Thus, it is difficult to accurately define object detection zones and, thereby, reduce false detections in SOD systems that use edge emitting laser diodes. Furthermore, edge emitting laser diodes themselves are relatively expensive and have relatively slow response times. Because of the orientation of the emitted beam, edge emitter laser diodes cannot be mounted in standard surface mount packages, further adding to the cost of their use in SOD systems. The high cost and low performance of edge emitting laser diodes results in a higher overall cost and diminished functionality for these prior art SOD systems which has greatly limited their SOD systems market penetration.
What is needed, then, is a vehicle mounted object detection system with a laser light source that is less expensive, provides increased accuracy, and that can be manufactured using conventional methods of assembly of surface mounted electronic components.